1. Field of the Invention
The present invention relates to a display device such as a liquid crystal display (LCD) device, and more particularly, to an apparatus and method for driving a display device, to obtain a rapid speed in a calculation circuit for converting data of three colors to data of four colors.
2. Discussion of the Related Art
In general, a cathode ray tube (CRT), which is one type of flat display devices, cannot satisfy the demands for compact size and lightweight due to its big size and heavy weight. Thus, various display devices, for example, a liquid crystal display (LCD) device using electric field optical effect, a plasma display panel (PDP) using a gas discharge, a filed emission display device, and an electroluminescence display (ELD) device using an electric field luminous effect, have been studied to substitute for the CRT.
The LCD device includes a TFT substrate, a color filter substrate and a liquid crystal layer. The TFT substrate is provided with a plurality of liquid crystal cells in pixel regions defined by a plurality of gate and data lines, and a plurality of thin film transistors, wherein the thin film transistors functions as switching devices for the liquid crystal cells. The color filter substrate having a color filter layer is positioned opposite to the TFT substrate at the predetermined interval. Then, the liquid crystal layer is formed between the TFT substrate and the color filter substrate.
In the LCD device, an electric field is formed in the liquid crystal layer according to a data signal, thereby obtaining the desired picture image by controlling the transmissivity of light passing through the liquid crystal layer. The data signal is inversed by frame, line or dot, so as to prevent the deterioration generated when the electric field of one direction is applied to the liquid crystal layer for a long time.
The LCD device realizes a color picture image by mixing the light of red, green and blue from three color dots of red, green and blue. However, in case of the general LCD device having sub-pixels of the three color dots of red, green and blue, the light efficiency may be lowered in the LCD device. Specifically, color filters formed in the sub-pixels of red, green and blue transmit one-third of the light, whereby the entire light efficiency is lowered.
In order to maintain the color realization ratio and to improve the light efficiency of the LCD device, Korean Patent Application No. P2002-13830 (LCD device) discloses an RGBW type LCD device which includes a white color filter W as well as red, green and blue color filters. Also, Korean Patent Registration No. 464323 (apparatus and method for changing brightness of image) discloses an apparatus and method for converting three-color input elements to four-color elements.
However, when outputting red, green and blue values in these LCD devices, it requires a calculation circuit. Therefore, it has the disadvantage such as a slow operation speed.
Also, the apparatus and method for converting three-color input elements to four-color elements include a plurality of division calculation circuits.
In comparison with the operation speed of addition, subtraction and multiplication, the operation speed of division is slower. Thus, in order to perform the real time calculation, it has clock latency in correspondence with clocks by using a pipeline structure. Accordingly, if the division calculation increases, the clock latency of the entire calculation also increases, whereby it requires a plurality of registers. As a result, the apparatus and method for enhancing brightness of image has the disadvantage of the low operation speed due to the plurality of division calculation circuits.